The brown blob coupling caps are pretty lousy, but most of the other caps that came in the Sunns are good stuff, and I wouldn't replace them unless they were leaking DC. The brown blobs have lousy ESR and probably still function fine but pretty much any new cap will sound better than those. In my 1970 Sonic 1/200S that I rebuilt several years back, I replaced the coupling caps with a mixture of Orange Drop 716P's, Orange Drop 225P's, and Mallory 150's. I used a couple Solens to go from the phase inverter to the power amp for a bit more high end. In mine, the Cornell Duplier greenies were leaking DC, so they were replaced. In some others than I've worked on in the past, the greenies and the Black Cats were still working fine so I left them and just replaced the brown blobs with Orange Drops. If I was to use the amp for guitar (not going to happen for me as I hate Sunns for guitar..haha) then I might go with more polyester caps instead of polypropylene, but for bass, the polypropylenes work great.
I was able to find all the values needed, though I think the .0075uf were polyester Orange Drops...probably surplus 225P's that I found locally. AES used to carry a wider selection like a .0075uf and a .25uf in the 6PS polyester Orange Drop line, but they don't anymore. I'd check around at local surplus shops and see if you can find something in those values.
Greg
